The invention concerns a system for automatic following guidance, particularly for heavy-traffic following guidance, of a motor vehicle, comprising
an electronic cruise, braking and steering control/regulation system,
an environmental image acquisition unit equipped with a video camera and downstream image analysis and generating signals that can be input to the electronic cruise, braking and steering control system at least for automatic guidance along a marked traffic lane, and/or
an environmental detection unit operating on the basis of detected reflections of emitted electromagnetic radiation, and
a spacing and relative-speed detection unit that detects a spacing and a relative speed with respect to a leading vehicle selectable on the basis of signals generated by the environmental image acquisition unit and generates in each case a corresponding spacing and relative speed detection signal.
A similar system is described in U.S. Pat. No. 5,684,697. In the known system, image frames supplied by the video camera are digitized and are processed by a computer, which automatically controls or regulates the steering, acceleration, deceleration and braking of the vehicle within specified criteria. The automatic steering of the vehicle is based on the acquisition of images of stripe-shaped road markings, whereas the automatic speed control or regulation is based on detecting the location of a leading vehicle within the marked traffic lane.
By contrast, a further system, known from U.S. Pat. No. 5,572,449, employs speed signals that are detected both by a vehicle to be controlled and by a preceding, leading vehicle and are exchanged via a communication system in order to determine the relative speed between the two vehicles and to generate control signals that stabilize the speed and thus a safe following distance of the trailing vehicle with respect to the leading vehicle, and further, to control the steering in such a way that the trailing vehicle can follow the preceding one. A disadvantage here is that all vehicles traveling in a column must be equipped with the same system.
A further system, known from U.S. Pat. No. 5,245,422, like U.S. Pat. No. 5,684,697, employs a video camera and its images, processed by an image processor, to define the lane markings on the road and the position of the vehicle with respect thereto. The combined engagement of a cruise control switch and a steering control switch are [sic] detected and used to initiate the processing of the image data and automatic steering of the vehicle. However, the automatic maintenance of a given distance from a preceding, leading vehicle is not described in the above U.S. No. Pat. 5,245,422.
In heavy-traffic situations, it often happens that one vehicle in a column follows another traveling at a lower speed, e.g. less than 20 kmh, in the same lane. In such situations, the driver""s attention is focused primarily on maintaining a given distance from the preceding driver, so as to have an adequate stopping distance in the event of sudden braking. At such low speeds and with the vehicles moving steadily, minor corrections, if any, are all that is needed in order to steer the vehicle. When these driving situations persist for a relatively long period of time, they often cause fatigue or distraction on the part of the driver, since they claim only a small share of his attention.
The object of the invention is to make possible a system for automatic following guidance, particularly for heavy-traffic following guidance, of a motor vehicle, which can effectively ease the burden on the driver in certain situations, for example in heavy-traffic situations, by taking over lateral guidance and spacing guidance with respect to a leading vehicle.
A prerequisite for such a system for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle, is an automatic cruise control system with a xe2x80x9cstopxe2x80x9d and xe2x80x9cgoxe2x80x9d function, which under predetermined conditions makes it unnecessary for the driver to operate the brake, gas and clutch pedals and which, in dependence on specific situations, permits automatic stopping, starting and travel up to a defined limiting speed, independently of actions by the driver. A further prerequisite for the functioning of such a system for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle, is an automatic steering control or regulation system that can impose steering movements and/or steering torques on the steered wheels independently of any actuation of the steering wheel by the driver. A further prerequisite of the system according to the invention for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle is the presence of lane markings and a leading vehicle that is within the lane markings and is moving slowly in the case of heavy traffic. The system vehicle follows the leading vehicle for as long as it travels within the lane markings and below a limiting speed. If the leading vehicle removes itself from consideration, for example by leaving the lane or exceeding the limiting speed, the system deactivates. The same applies when the lane can no longer be detected by means of the environmental image acquisition unit equipped with a video camera and a downstream image analyzer, for example if lane markings are no longer present or are ambiguous. A warning signal informs the driver of each impending deactivation of the automatic following guidance system, particularly of the heavy-traffic automatic following guidance system.
The system of the invention for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle comprises selection and decision means which, on the one hand, decide on the basis of parameters that can be input by and/or are dependent on the driver and on the basis of conditions determined automatically by the system whether automatic following guidance is feasible or whether manual cruise, braking and steering control/regulation must be performed by the driver, whether only automatic guidance along a marked, recognized lane or following guidance based on a recognized leading vehicle or a combination of these types of automatic guidance is feasible, and which, on the other hand, also select on the basis of parameters that can be input by and/or are dependent on a driver and on the basis of conditions determined automatically by the system which of the parameters are to be used to decide between automatic and manual following guidance, and which, if automatic following guidance is performed, select the regulating parameters for cruise, braking and steering regulation.
In the system according to the invention for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle, the following switching conditions are realized in the form of AND criteria:
The system is active only when the automatic cruise control/regulation system with xe2x80x9cstopxe2x80x9d and xe2x80x9cgoxe2x80x9d control is active. The automatic xe2x80x9cstopxe2x80x9d and xe2x80x9cgoxe2x80x9d control requires a release by the driver in order to start moving again after a stop.
The lane markings have been detected unequivocally by the environmental image acquisition unit. I.e., the lane recognition system detects, for example, two broken lines spaced up to 12 m apart, for example. Additionally or alternatively, sufficiently high curbs, for example projecting at least 10 cm above the surface of the road, can be recognized as the lane boundary for short distances.
The leading vehicle is present and has been recognized unequivocally by the environmental image acquisition unit.
The speed of the leading vehicle is below the limiting speed, i.e., below 20-30 km/h, for example.
The selection and decision means of the invention further realizes the following deactivation conditions as xe2x80x9cORxe2x80x9d criteria:
if the activation conditions are not or are no longer present;
if the driver performs a steering action beyond a certain steering torque or a floor-pedal action, i.e., an action on the brake pedal, gas pedal or clutch pedal;
if the driver deactivates the system for automatic following guidance of a motor vehicle, e.g. by actuating a switch. In this case the system must deactivate immediately;
if lane markings are not or cease to be present or cannot be recognized unequivocally, or if the lane markings are present but there is no leading vehicle. In this case, after outputting a deactivation warning signal, the vehicle brakes to a stop with no action by the driver and the system deactivates after a defined waiting time, e.g. 1-2 s. The automatic braking operation is interrupted by any intervention on the part of the driver, whether on the steering wheel or on the accelerator or brake pedal, or by deactivation of the automatic cruise control;
if the limiting speed is reached. In this case, the system initially remains active and the system vehicle does not accelerate past the limiting speed. If the leading vehicle then leaves the control range of the system by increasing its speed, the system deactivates, after first giving a deactivation warning signal, since there truly is no longer a leading vehicle in this case.
Regardless of the manner of deactivation, the driver must be able to assume control of the vehicle at any time. Optionally, the automatic cruise control/regulation system can be deactivated along with the deactivation of the automatic steering control/regulation system.
The system of the invention for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle, can be arranged to generate the following information signals and warning signals:
information signals can be generated if implausible driving by the leading vehicle within the recognized lane marking is detected, for
example if the leading vehicle swerves or starts to make a lane change.
A deactivation warning can be generated before each system deactivation.
The system of the invention for automatic following guidance, particularly for heavy-traffic automatic following guidance, of a motor vehicle permits a modular and expandable, hierarchically organized controller structure that offers situation recognition by the system and/or by the driver and situation-dependent decision-making and selection via the control/regulating mode, i.e., manual or automatic control, selection of the type of control or regulation, i.e., lane following or following behind the leading vehicle, and selection of the controller parameters and the setpoint values for the regulating system.
Also optionally provided is a driver-type recognition unit that brings about driver-adaptive adjustment of the system. The driver has the highest priority in every case and can assume control of the system at any time, since he is always in the monitoring loop.
The claimed environmental recognition unit preferably operates by means of radar (Radio Detection and Ranging) and/or lidar (Light Detection and Ranging) emission.
A preferred embodiment of a system according to the invention for automatic following guidance of a motor vehicle is described in more detail hereinbelow with reference to the drawing. The invention is elucidated in particular with reference to automatic following guidance in heavy traffic.